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Instantaneous rate of change of a sphere

  1. Mar 2, 2008 #1
    1. The problem statement, all variables and given/known data
    Find the instantaneous rate of change of V with respect to r when r=5 micrometers

    2. Relevant equations


    3. The attempt at a solution

    would you just take the derivative? and if so, wouldn't it just be zero, because it comes out to be a real number, right? but that doesn't seem right...
  2. jcsd
  3. Mar 2, 2008 #2


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    Science Advisor
    Gold Member

    What is the derivative of V=4/3pi(r^3)? Now what would the value be at r=5micrometers? Not zero.
  4. Mar 2, 2008 #3
    ooh, im an idiot, thanks
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